Whether we want to admit it or not, the good old Mil-spec bolt has had a good run, but it's long past its retirement age, and the JP EnhancedBolt™ is there to pick up where it left off.
Material matters, and the Carpenter 158 steel of the standard Mil-spec bolt is suboptimal for such a high-load application leading to a life expectancy of only about 6,000 rounds. In fact, standard bolts will start to show stress cracks on the locking lugs adjacent to the extractor cut after only 3,000 rounds while cracking at the cam pin hole and weak extractor spring tension only add to the problems of the Mil-spec bolt. Fine enough for its time, the material used in these standard bolts is simply not the best choice by today's standards.
The SAE 9310 of the JP EnhancedBolt™ is a superior steel alloy in virtually every way compared to the C-158, whether in its resistance to structural failure or life expectancy, both of which far exceeding the Mil-spec. Just as with the transmission gears for Formula 1 racers which are also made from 9310, the operational demands of a bolt assembly are ideally suited to this state-of-the-art material, with actual full-auto endurance torture tests prove it.
Beyond its material advantages, the design of the JP EnhancedBolt™ boasts many other advantages, including the addition of material around the cam pin hole to eliminate this inherent weak point of the bolt design itself. Each bolt also comes assembled with our proprietary Enhanced Ejector, Enhanced Extractor (.308 and Grendel) and Enhanced Gas Rings for improvements in every subcomponent. Yet even with these advanced components, all EnhancedBolts™ (excepting our .308 high pressure model, for obvious reasons) are fully compatible with the readily available Mil-spec subcomponents, including a standard configuration extractor—all the benefits of a state-of-the-art proprietary platform with none of the inconvenience.
For anyone using .308/7.62 AR-type rifles, it is common knowledge that many factory rounds exhibit excessive primer flow and/or ejector smear. At its core, this is a result of ammo development being done by manufacturers only for manual platforms without testing in semi-auto platforms. Some rifle manuals even record the maximum recommended load data beyond the functional range of these rifles. Unfortunately, these issues will persist until the manufacturers of ammunition realize that an AR platform requires a unique pressure curve to allow for both accuracy and reliability.
Manufactured to the exacting standards of our standard bolt offerings, the High Pressure EnhancedBolt™ design represents a giant leap forward in alleviating the problems traceable to over-pressured loads—namely primer flow, ejector smear, extraction issues, and ignition reliability. In combating these problems, this new bolt design opens up a much broader range of ammunition compatibility and load density in the AR .308/7.62 and other variants such as 6.5mm or 6mm calibers in this platform.
The critical advancement of this bolt comes in the reduced diameter firing pin orifice that precisely accommodates the .062" tip of our proprietary low mass firing pin. This modified relationship virtually eliminates primer flow and the possibility of pierced primers on any SAAMI or NATO specification ammunition while the reduced mass of the firing pin also improves lock time and ignition reliability with hard primers due to the concentration of kinetic energy on a smaller impact area. This is especially advantageous with some aftermarket match-type fire control systems that may use reduced-power hammer springs.
Among its other enhancements, the .308HP bolt features an improved ejector pin hole and modified ejector to mitigate case head extrusion and frequent brass shavings. The JP Enhanced Extractor eliminates virtually all extractor-related failures while the JP Enhanced Gas Rings provide a more reliable, lower friction gas seal with longer lifespan.
While ultimately every end user needs to be aware of the ammunition limitations of their large-frame AR, the JP .308HP bolt offers multiple advancements to vastly increase the ammunition and operational abilities of the platform.
Disclaimer: The JP .308HP bolt does not allow for the use of excessive pressure, overloaded ammunition that exceeds SAAMI specifications. When evaluating new ammunition, always start on the low- to mid-range of any published load data and work up. A good indicator of working pressure is the primer retention on the subsequent loading of a case. A noticeable loss of primer pocket tension indicates that your ammunition has excessive pressure and has overworked the case.
Much like our original EnhancedBolt™, we deemed it necessary for the function and reliability of our rifles to produce 6.5 Grendel and 6.8 SPC II/.224 Valkyrie bolts that were both consistent in their dimensions and in line with our quality control standards. These versions of our EnhancedBolt™ includes all the benefits of their .223 cousin: 9310 constructions, extra material around the cam pin hole, improved lug geometry and the inclusion of our JP Enhanced Extractor and Enhanced Gas Rings. While backwards compatible to standard extractors, EnhancedBolts™ in these calibers include our proprietary extractor for superior function and elimination of extractor-related failures. Each bolt is head-spaced to ± .0005" to ensure cross-compatibility between properly chambered barrels. If you're working up a new 6.5G, 6.8 SPC II or .224 Valkyrie project, don't take a chance on this critical component.
The JP Enhanced Extractor is another example of our refusal to have the performance of our rifles hamstrung by the poor or inconsistent quality of the standard subcomponents on the market. A complete redesign of the DPMS-pattern extractor, our Enhanced Extractor eliminates premature ejector failures and other malfunctions resulting from the extractor not clearing the case rim. The articulation required to clear the case rim has been minimized for reliable, in-battery closure while a new composite spring system allows for consistent extractor-to-rim engagement to ensure reliable extraction and improved resistance of extractor disengagement. More consistent metallurgy also lends to a longer duty life compared to the standard alternative.
If your rifle continues to have extraction related issues with this extractor, you can be assured that the problem lies elsewhere. If your rifle does not have other exacerbating issues, this should be the last extractor you need to buy.
See our discussion on extraction failures included with the Enhanced Extractor instructions to help you more fully diagnose your rifle.
As a replacement for traditional three-piece gas rings, our Enhanced Gas Rings utilize a one-piece design similar to the Mcfarland rings. Unlike the Mcfarland rings, though, our precision-ground gas rings are engineered to precisely suit either small-frame or DPMS-patterned carrier group components such as our own JP EnhancedBolt™.
After testing numerous minute grind callouts, the final JP Enhanced Gas Rings spec is the perfect balance of a solid gas seal with a very low-friction relationship between rings and bolt carrier. Reducing the resistance between these components directly results in an overall increase in the rifle's operational window while the edge of the rings utilizes the cycling action itself to scrape the walls of the carrier, helping shed fouling with every shot.
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